Wireless communication systems are well known in the art. Generally, such systems comprise communication stations, which transmit and receive wireless communication signals between each other. Depending upon the type of system, communication stations typically are one of two types: base stations or wireless transmit/receive units (WTRUs), which include mobile units.
The term base station as used herein includes, but is not limited to, a base station, Node B, site controller, access point or other interfacing device in a wireless environment that provides WTRUs with wireless access to a network with which the base station is associated.
The term WTRU as used herein includes, but is not limited to, a user equipment, mobile station, fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment. WTRUs include personal communication devices, such as phones, video phones, and Internet ready phones that have network connections. In addition, WTRUs include portable personal computing devices, such as PDAs and notebook computers with wireless modems that have similar network capabilities. WTRUs that are portable or can otherwise change location are referred to as mobile units. Generically, base stations are also WTRUs.
Typically, a network of base stations is provided where each base station is capable of conducting concurrent wireless communications with appropriately configured WTRUs. Some WTRUs are configured to conduct wireless communications directly between each other, i.e., without being relayed through a network via a base station. This is commonly called peer-to-peer wireless communications. Where a WTRU is configured to communicate with other WTRUs it may itself be configured as and function as a base station. WTRUs can be configured for use in multiple networks with both network and peer-to-peer communications capabilities.
One type of wireless system, called a wireless local area network (WLAN), can be configured to conduct wireless communications with WTRUs equipped with WLAN modems that are also able to conduct peer-to-peer communications with similarly equipped WTRUs. Currently, WLAN modems are being integrated into many traditional communicating and computing devices by manufacturers. For example, cellular phones, personal digital assistants, and laptop computers are being built with one or more WLAN modems.
A popular local area network environment with one or more WLAN base stations, typically called access points (APs), is built according to the IEEE 802.11 family of standards. An example 802.11 Local Area Network (LAN), as shown in FIG. 1, is based on an architecture, wherein the system is subdivided into cells. Each cell comprises a Basic Service Set (BSS), which comprises at least one AP for communicating with one or more WTRUs which are generally referred to as stations (STAs) in the context of 802.11 systems. Communication between an AP and STAs is conducted in accordance with the IEEE 802.11 standard that defines the air interface between a wireless STA and a wired network.
A wireless LAN (WLAN) may be formed by a single BSS, with a single AP, having a portal to a distribution system (DS). However, installations are typically composed of several cells, and APs are connected through a backbone, referred to as a DS.
A mobile ad-hoc network (MANET) is also shown in FIG. 1. A MANET is a self-configuring network of mobile routers (and associated hosts) connected by wireless links—the union of which form an arbitrary topology. The routers are free to move randomly and organize themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. Such a network may operate in a standalone fashion, or may be connected to the larger Internet.
An interconnected WLAN, including the different cells, their respective APs and the DS, is seen as a single IEEE 802.11 network and is referred to as an Extended Service Set (ESS). IEEE 802.11 networks typically use a Carrier-Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol to exchange information wirelessly between nodes (or STAs) of the WLAN network. In this framework, STAs desiring to transmit must contend for access to the wireless medium. The contention mechanism involves waiting for the medium to remain idle for a certain period of time (according to a set of rules prescribed by the standard) before transmitting a data packet. The time it takes a node to access the channel and transmit its packet increases as the number of stations and data traffic increases. Congestion in such a system can occur when the time to gain access to the medium becomes intolerable due to too many stations competing for the same medium.
Due to the nature of the CSMA/CA protocol, and considering that most transmissions are best effort, it is quite difficult to determine when a system is classified as experiencing congestion. Determining congestion in such an complex system is not a simple task, as one choice of metrics could indicate congestion while another metric will not.
Several metrics that can be used to indicate congestion include: collision rate, channel utilization, i.e., the time that the medium is busy, etc. However, these metrics, taken individually do not necessarily give a true picture of the congestion. For example, the channel utilization metric does not give an accurate picture of the congestion situation. One station can be alone on a channel and transmitting all the time. In this case the channel utilization metric would be high. It may seem like the system would not be capable of supporting any more traffic from other stations. However, if a new station were to access the channel, it could still experience good throughput by virtue of the CSMA/CA mechanism, as the channel would then be equally shared between the two stations. A system is in fact congested when there are a number of stations contending for the same channel at a given time and experiencing severe delays due to the longer time each station has to wait for access to the medium, as well as the higher number of collisions.
In another aspect, there is currently limited network management functionality, particularly in systems compliant with the IEEE 802.11 and IEEE 802.11k standards. The inventors have recognized that there are certain limitations to the usefulness of channel loading information presently employed in the context of network management. There is also a need for an improved method of achieving better network management after considering the limitations of using channel-loading measurements. This present invention provides enhanced network management associated with the IEEE 802.11 and IEEE 802.11k standards in the context of channel loading information.